Tips on DuraSpark modules

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Ford fans like to identify the DuraSpark modules
by their grommet color (where the wires enter the
module). There are RED, BLACK, YELLOW, GREEN, BLUE
and even ORANGE ones.

The 200 engine usually has modules with BLUE grommets.
These have 2 connectors on them, one for the power
and one for the distributor pickup. These are good,
reliable replacements for point-type units, especially
when used with Ford coils.

The high-performance models have a YELLOW grommet.
These have 3 connectors on them: the extra 3-pin plug
connects to an ATMOSPHERIC PRESSURE SENSOR, although
the module will work fine without this extra gadget.

Ford used 2 types of these pressure sensors. One type
has 1 vacuum hose connection on it and the other has 2.
The one with 1 connection is the "absolute pressure" or
"barometric pressure" type. The other is a "relative
pressure" type. Both are useful for different things.
The 1-hose type is common on high-altitude Fords and
helps correct for thin atmosphere. The other was found
on Lincolns and Mercurys everywhere. These sensors are
really just vacuum switches.

The sensors work like this: when the sensor is plugged
into the module, it advances timing 2 degrees over the
regular static setting. When high vacuum is applied to
the sensor, it causes the DuraSpark module to
electronically advance the timing (about 4-6 degrees).
When this vacuum goes away, the timing drops back to
'nominal' (i.e., 2 degrees of advance) after about 3
seconds. This was designed for emission controls.

You can use this to either improve your gas mileage or
improve your HP. To improve gas mileage, connect a 1-hose
switch to MANIFOLD vacuum for extra advance during light
throttle (in-town) driving. To improve HP, connect it
to THROTTLE PORT vacuum and retard your static timing
by about 2-4 degrees (for instance, if your normal stock
advance is 6 degrees, use 4 instead).

Using the 2-hose sensor is slightly more complicated: one
hose goes to the vacuum source you wish to use and the
other can be left open or run to the opposite vacuum
type. Watch the action with your timing light: if the
spark is not advanced at idle, then you are connected
for extra HP. If it does advance at idle, you're
connected for better MPG. Connecting the ON side to
manifold and the OFF side to port vacuum will improve
mileage while retarding spark slightly under heavy
throttle, which can help with high compression ratios.
 
A little hard data for those curious about the
properties of the "Yellow Grommet" Duraspark II: keep
in mind that mine is a "high altitude" car, built by
Ford for use in Colorado. The engine sticker says,
"Ign Timing 14* BTDC at 650 RPM". I had looked inside the
distributor and found the advance slot to be 13 degrees,
which would seem to add up to [(13 x 2) + 14] = 40 degrees.
Since this seemed like a LOT of advance to me, I followed
a local Ford dealer's instructions to get these results.

I unplugged the vacuum sensor (I'm using the "Absolute
Pressure" (a.k.a. "Barometric Pressure") sensor. I unplugged
the vacuum to the distributor and the vacuum sensor, which
is connected to manifold vacuum on this car. I also unplugged
the vacuum sensor wiring at the 3-pin plug. Then, I set the
timing to 6 degrees BTDC and idle speed to 500 RPM to make
sure the distributor springs were fully retracted. Then, with
no vacuum connected to the sensor, I plugged it into the
Duraspark. The timing retarded itself to 3 degrees BTDC (it
dropped from +6 to +3). Then I connected manifold vacuum to
the sensor and the timing advanced itself to 14 degrees.
The engine, of course, increased to 650 RPM which -duh-
is the idle spec on the engine sticker. Snapping the throttle
open gives a very crisp response and the timing remains high
through 3000 RPM. When the throttle was closed again, the
timing stayed at 14 degees.

Then, I connected throttle port vacuum to the sensor. The
timing dropped back to 3 degrees and the idle to 500. When
I snapped the throttle, there was a more sluggish initial
response, but then it rose more quickly until it shot past my
desired 3000 RPM test point (my dwell tach goes to 3000).
When I closed the throttle, the engine dropped to idle more
quickly because the timing dropped back to 3 degrees and
stayed there.

There was an observable delay to the timing retard, about
3 seconds or so. To see this, I connected, then disconnected
the manifold vacuum to the sensor. The timing would advance
immediately upon getting vacuum, but it would drop back
about 3 seconds after the vacuum was removed.

This all adds up to 33 degrees advance at full throttle.
When full throttle is applied and the manifold vacuum goes
to near 0 the advance adds up to [(13 x 2) + (14 - 7)] = 33
degrees max advance.

This engine never knocks, even with an "apparent" 14 degree
static timing. The actual starting advance is 3 degrees,
since the Duraspark retards during the start cycle.
 
Mark,

Thanks for the DS module info... your experience w/ high altitude timing is consistent with my own; after having moved to the mountains I've had to run waaay more timing than I was accustomed to at sea level. With my points distributor I have to wrench in more timing several times between North Platte and Cheyenne...

Needless to say the motor has fits on the way back down the mountain, especially if I've still got 85 octane in the tank!
 
Hi, SuperM;

The NHRA and other racing groups here recommend 1 degree advance for every 1000 feet gained altitude. I have measured some of the
all-electronic cars at 45 degrees advance just by "tricking" the vacuum
sensors! Of course, they modify the fuel mix to match.

One oddity remains in my garage, though, that I've never understood. I have a 1967 Fastback LTD with a 390 'H' engine. The OEM distributor has 1 advance slot size (both sides are 20 degrees) and static timing of 6 degrees. It's TERRIFIC in the mountains and even down to 300 feet in Missouri it never knocks. It uses throttle port vacuum on the distributor, which has 30 degrees vacuum available. The static timing is 6* on top of all this. Yet, it never knocks or overheats. This one's always been an enigma to me... :roll:
 
Sorry to go off on a tangent!

FE-block engines are interesting in that they often run quite long duration camshafts, being post emission era engines really. I've heard stories of drag racers using 428 Super Cobra Jets with stock 11:1 compression and superchargers in the days of 120 Sunoco gas. If the cam timing can blead off some effective compression, then knocking is less prevelent. The intake runners also were interesting on that engine...not like the huge ported 335 and 385 engines which almost needed arrows to tell the air/fuel mix which way to go!

A Ford engineer in Australia found that most bearing failure in the later polyspheric/canted valve Cleveland engines was due to incipient knock which was just out of the treashold of hearing. But those engines carried lots of compression, and around 252 degrees of duration. Huge ports, which promoted fuel drop-out below 2700 rpm. And often with quench heads which interupted incoming gas flow, interupting an easy flame front. Detonation city!

But, that was in the 70s, and you know what they say - "Even I remember the 70s, I WAS THERE!"


Edit:
being post emission era engines really
pre pre pre-emission engines. Five points off and go to back of class
:cry:
 
Hey there, Fanatic;

Just ask for the 1979 T-Bird "Yellow Grommet" Duraspark module. Better yet, go to a junkyard where they cost 5 bucks for a real FoMoCo - and you can get the trigger pickup, vacuum sensor, wiring connectors, etc., probably for free!

The Ford Duraspark modules are more often identified by their color than by their application. I've seen 4- and 6-cylinder engines with black, green, yellow and blue. I'm not sure how Ford designed their systems, because they seem to be all mixed up. Even the wiring schematics for the cars show all different types in with the engines! :roll:
 
Taking this one step further...

I'm no electrical genius, but I'm sure there is a switch/relay/bypass that you can wire up to switch inside the car that would allow you to switch between HP and Mileage mode.

Slade
 
Great posts on the DuraSpark boxes. Thanks.

re. the Cleveland heads:
Wouldn't those monstrous ports be an advantage on a custom-EFI Windsor small block(bored & stroked to 435"), since they'd be merely 'dry runners'? Just a thought.

J.R.
 
Off the topic a little :oops: , but I personally believe, based on the common fireing order (between bigger Fords, post 80 US302's and post 88 us351W's), the use of similar SVO A3 heads in NASCAR and AVESCO, and the fact that they were really Chevy BB copies with flatter angles, that Cleveland heads are perfect for big fuel injection engines. The lack of development for these engines after they got pensioned off for light duties in Ozzy from 74 to 83 is a crime. The 302/351C's down here did get Duraspark ignition systems from 1976 onwards, but I'll bet they were just regiggs of the 351M/400 engines units. Early engines were very detonation prone...racers and engine builders felt they moved around a lot in the block and crank, but detonation sets in very savagely in a canted valve engine. Due to a poorly conducted headgasket replacement by a former owner, my alloy head crossflow Falcon suffered such severe detonation after ahead gasket let go, that the intake seat surround (throat) was melted! My wife said there were no warning signs, it just happened while cruising up the hill to our place in Dunedin. About 12 miles, 1000 foot climb, and it was deader than dead.

Possibly older wedge and bathtub heads have a less sudden combustion event, and the electronic ignition can be set fairly aggressively without damage. After 1976, our Aussie Falcons I6's got refitted with Bosch electronic systems, and were not the same as the American ones. This was another case of a small market not having the market share to invest in the American set up. In any case, the cross-flow head fouls the fitting of a US 200/250 DurasparkII unit.
 
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